Calling this function in Noesis 4.0.0 / 4.0.1 results in my application crashing about 50% of the time.
MediaElement.SetCreateMediaPlayerCallback(GEMediaPlayer.Create, null);

AI Investigation:

What the stack shows
• App.Main → app.Run() (line 370) → NoesisApp.Application.Start → Window.Init → _view = GUI.CreateView(this); (Window.cs line 250).
• View.CreateCPtr calls into Noesis.dll, which then reads address 0xFFFFFFFFFFFFFFFF.
• GUI.CreateView hands the UIShell.MainWindow element tree, loaded from MainWindow.xaml, to the native view. Noesis then hooks up that tree: it applies styles, resolves resources and connects to the managed MainWindow object. That's where it crashed.
What I checked
• Noesis.GUI.dll and Noesis.App.dll are both version 4.0.1.18228, so the two managed libraries match each other.
• MainWindow isn't disposed (IsDisposed = false). PPAA = true, Samples = 1, and the render context is RenderContextWGL.
• The only exception before the crash was a first-chance NLog.NLogConfigurationException. It's probably unrelated, but it means the logging setup failed.
• There was no Noesis log output before the crash, so nothing points to a specific XAML or resource error.